This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Wireless LANs and PANs
01204325: Data Communication and Computer Networks
PCF – Point Coordination Function (controlled access)DCF – Distributed Coordination Function (random access)
13
CSMA/CA Used by 802.11 Basic CSMA/CA not enough
"Hidden Terminal Problem"
A B C
14
CSMA/CA With RTS/CTS
RTS
CTS
Data
ACK
A B C D
NAVNAV
NAV Network Allocation Vector
(Virtual Carrier Sensing)
15
IEEE 802.11 and Wi-Fi IEEE 802.11 provides most of the
standards A group of vendors who build
wireless equipment formed the Wi-Fi Alliance A non-profit organization that tests
and certifies wireless equipment using the 802.11 standards
Wireless PANs: Bluetooth
17
Bluetooth Standard Wireless Personal Area Network
technology Designed for connecting devices with
different functionalities: Telephone, mouse, keyboard, camera,
etc. Standard IEEE 802.15.1
18
Bluetooth Piconet
19
Bluetooth Scatternet
20
Bluetooth Layers
21
Bluetooth Communication Single slave
22
Bluetooth Communication Multiple slaves
Low-Rate Wireless PANs:
IEEE 802.15.4
24
IEEE 802.15.4 IEEE standard for Low-Rate
WPAN (LR-WPAN) applications Low-to-medium bit rates Moderate delays without too
strict requirements Low cost, low energy
consumption Applications
Home automation and security systems
Smart metering Wireless data collection
25
868MHz (20 kbps)
2.4 GHz
868.3 MHz
Channel 0 Channels 1-10
Channels 11-26
2.4835 GHz
928 MHz902 MHz
5 MHz
2 MHz
2.4 GHz PHY
IEEE 802.15.4 Physical Operating frequency bands
915 MHz (40 kbps)
2.4 GHz (250 kbps)
26
IEEE 802.15.4 MAC Single channel at any one time Combines contention-based and
schedule-based schemes Asymmetric: nodes can assume
different roles
27
IEEE 802.15.4 Devices Full function device (FFD)
Any topology Network coordinator capable Talks to any other device
Reduced function device (RFD) Limited to star topology Cannot become a network coordinator Talks only to a network coordinator Very simple implementation